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Television
Television or TV is a telecommunication system for transmitting and receiving moving pictures and sound. The receiving device is also called TV or''TV,'' or full television . The television is in the 20th century has become a major mass medium that reaches billions of people. Initially, the images transmitted were only inblack and white , but later was broadcast in color. This required a new kind of television needed: the color . After the analog television came the digital television . The latest innovation is the 3D television , a three-dimensional image displays. Content * 1 History ** 1.1 Mechanical line: the Nipkow disk ** 1.2 The electronic television ** 1.3 Important people in the development of TV technology in the 19th and 20th centuries ** 1.4 Development in the Netherlands and Flanders * 2 Technology ** 2.1 Television picture tube ** 2.2 LCD television ** 2.3 Plasma Television ** 2.4 Receiving television programs History The development of the television initially proceeded along two different lines: a rested according to both mechanical and electronic principles and which in a second purely electronic principles. Of the latter line, which in the United States came into being, all modern televisions are derived, but this had not been possible without discoveries and insights from the mechanical systems. Mechanical line the Nipkow disk The electromechanical television that Paul Gottlieb Nipkow developed and patented in 1884 was the basis of these, the so-called Nipkow disk . In this rapidly rotating flat disc were small holes arranged in a spiral pattern. The light and dark areas was washed with the aid of a photocell ( selenium cells ) is converted into an electrical signal. This started a neon lamp in the same sequence of light and dark the picture via a second synchronized rotating disk projected on a screen. However, it took until 1907 before the developments in the technology of the reinforcement tube design was practical. Another electromechanical system based on a mirror drum in both the camera and the monitor was developed around 1925 in the Soviet Union byLeon Theremin . Starting with 16 picture lines in the number of two years was increased up to 100 lines, after which it was surpassed in 1931 by thecathode-ray tube (CRT) of the RCA with 120 lines. In the period 1907-1910 showed Boris Rosing and his student Vladimir Zworykin a television system to the outside world with a mechanical mirror-drum scanner, and a cathode-ray tube in the receiver. This cathode-ray tube, an invention of Karl Ferdinand Braun in 1897, is a glass vacuum tube in which with the aid of an electron beam on the fluorescent end the image is projected . Rosing disappeared during the revolution of 1917, but Zworykin later went to work for RCA to build a genuine electronic television. A semi-mechanical analogue television system was first shown in London in February 1924 by John Logie Baird with a picture of Felix the Cat and a moving image by Baird on 30 October 1925. The company (Baird Television Development Company) realized in 1928, the first trans -Atlantic television signal, between London and New York . In 1932, Baird introduced the VHF television . The Baird system was approved by the BBC , which ended this practice in 1937 in favor of purely electronic television. The electronic TV Although the discoveries of Nipkow, Rosing, Baird and others were extraordinary, little is their technology still used in modern television: in 1934 against all electromechanical television systems were outdated. Already in 1908, Brit Alan Archibald Campbell Swinton the described concept of an electronic television system that makes use of the above-mentioned cathode ray tube. Braun suggested to use an electron beam in both the camera and the receiver, but his system was never built. A fully electronic system was first shown by Philo Taylor Farnsworth in the fall of 1927. Farnsworth, a Mormon farm boy from Rigby ( Idaho ), made its first system at the age of 14 years. He discussed the idea with his teacher, who could think of no reason why the system would not work (Farnsworth would later credit this teacher, Justin Tolman, as providing key insights into his invention). He kept the idea at Brigham Young Academy (now Brigham Young University) pursue. At the age of 21, he showed an operating system to its own laboratory in San Francisco . His breakthrough television freed from its dependence on spinning disks and other mechanical parts. All modern TVs of the tube are directly derived from its design. Russian Vladimir Zworykin is sometimes cited as the father of electronic television for his invention of the iconoscope in 1923 and his invention of kinescope in 1929; his design was one of the first to develop a television system with all the properties of modern picture tubes. About the controversy on a first (Farnsworth or Zworykin) invented the modern television has yet to be debated on this day. Important people in the development of TV technology in the 19th and 20th century * John Logie Baird , an engineer who invented one of the first working television * Guillermo Gonzalez Camarena , an engineer who developed a system to broadcast color television * Alan Blumlein , a pioneer of television in the United Kingdom and creator of the stereo * Walter Bruch , a pioneer of television in Germany and developer of the PAL -inch TV * Alan Archibald Campbell-Swinton * Allen B. DuMont * Philo Taylor Farnsworth , inventor of the famous television depicting dont leather * Boris Grabovsky * Charles Francis Jenkins , a pioneer in the field of cinematography and one of the first inventors of television in the United States * Léon Theremin * Earl Muntz * Paul Gottlieb Nipkow , an inventor who is generally regarded as the founder of the television * Constantin Perskyi * Boris Rosing , a pioneer in the field of television * Ulises Armand Sanabria * David Sarnoff , a founder of the NBC * Kenjiro Takayanagi , a pioneer of television in Japan and builder of the world's first all-electronic TV receiver * Kálmán Tihanyi , a pioneer of electronic television, he made important inventions in the development of the cathode ray tube and the iconoscope * Vladimir Zworykin , a pioneer of television: he found a transmitting and receiving system of television based on a cathode ray tube Development Netherlands and Flanders * History of the Dutch TV * History of the Flemish television Technology There are three common types of display technologies: the LCD -inch TV, the plasma television and the CRT or CRT television. The LCD TV is relatively new, the plasma TV slightly older (introduction in the consumer market around 1995) and the CRT TV has been around longer (introduction in the Netherlands around 1951). This page explains the difference in technique between the LCD TV and CRT TV. CRT Television A television picture is divided into a large number of pixels in the colors red, green and blue. A television picture tube has a tube composed of phosphorescent dots on the screen in front and three electron guns mounted the tube back. There are separate guns for the color red, blue and green. By electrons with tremendous speed against the pixels shoot to illustrate these points, so they are visible on the outside of the display. Depending on the image to be formed, one point is tipsy less hard than the other making a difference in brightness in the image. Electrons, however, do not fly by itself to the front of the tube, you have to speed them up. By putting a high voltage of approximately 30 000 V (at 1-3 mA) on the tube, the electrons are pulled back from the guns and shot at the screen, towards the pixels. In order to be able to touch all the points of the display screen the electron beam must be deflected horizontally and vertically. For both the horizontal and the vertical deflection are electro-magnets which deflect the beams from the guns. Depending on which position the beam should be, it is more or less deflected. By the addition of a shadow mask which is located in front of the image plane points, it is ensured that the beam having red image information can only land on the pixels light up in red. The sieving action of this mask then prevents the beams having blue and green information on the red image dots are liable to enter. In order to obtain a random color, the colors red, green and blue mixed, through the colored pixels on a certain place in a certain ratio to leave lights on. The human eye is not able to distinguish these individual points at a greater distance and will see it as a particular color. In this way, can be generated a whole palette of colors. This process is repeated in Europe, 50 times per second (using the frequency of the mains power ), but by interlacing a half image will only be shown at each iteration - alternately the even and odd lines are shown. Because movie works with 24 frames per second, which can sometimes be played back a little too fast on television. In the past, film actors therefore an unnaturally high voice on television. LCD TV An LCD screen itself emits no light, but manipulates the ambient light or the light can shine through from the back. Each pixel (see text above) from the screen consists of two groups of liquid crystals (hence also the name). These crystals have the property that they twist depending on whether or no applied voltage, striking or transmitted light in polarization. If there is no voltage on one of the layers is, nothing happens and the light just by. However, when tension is put on, the light can no longer or worse (depending on the amount of voltage) through. Plasma television In a plasma television, the image points are formed by small gasontladingslampjes , somewhat similar to the principle of, for example, a fluorescent lamp. The right material the different colors emitted per pixel. In a plasma display, electrical energy is added to a gas mixture. Plasma is unstable and gives off the absorbed energy in the form of heat and an ultraviolet ray of light (photon). A phosphor layer converts the ultraviolet light into visible light. The color of this visible light is determined by the phosphorus. To more than 17 million different colors to make are red, green and blue colors generated. These colors blend to the desired color. 1 Receive TV programs Part of the television technology, the frequencies for receiving and transmitting. Antennas on the roof for television reception. With the introduction of cable television and satellite antennas virtually disappeared rake. For televisions are in the United Kingdom uses the ether frequencies between 470 and 860 MHz ( channels 21 to 69), whereas in the rest of Europe, also the channels 2 may be used up to and including 12. For use on closed cable networks are also other frequencies in use, those between 12 and 21 inliggen channel, the so-called S- and H-band. In the ether is to the trend from analog signal to DVB-T to switch, where only UHF-channels are used for.In the Netherlands all analogue terrestrial frequencies (VHF and UHF) already lapsed since 11 December 2006. The most famous of these were theLopikse channels 4, 27 and 30. In Flanders anno 2013 still broadcast analog television. Also on the cable is due to the introduction of DVB-C and wired internet trend to leave the VHF, S and H channels. In television, a black-and-white picture appears via amplitude modulation (AM) mounted on the carrier wave . The color information is associated with an auxiliary carrier wave and quadrature-amplitude-modulation (QAM) sent. This is the introduction of a color signal, the signal also to be received well in a black-white television, which processes only the first signal. To the bandwidth to keep the entire signal is limited to approximately 6 MHz, it is restzijbandmodulatie used, a special form of AM. The corresponding audio is sent on a subcarrier at a certain distance from the image signal. In most such cases frequency modulation used (FM). Since AM is much more sensitive to pulse signals than FM, will at lightning in the vicinity or the image are distorted slightly, but the sound remains mostly unaffected. Also, sources of ignition, such as mopeds may have this effect. Category:Consumer electronics Category:History of the television Category:Television Category:Video equipment Category:1927 introductions